This invention relates to a DC/AC converter for energizing a metal vapour discharge tube, in which the converter has two input terminals which are interconnected by means of a first series-combination of a first transistor, a load circuit which--in the operating condition--comprises the discharge tube, a primary winding of a transformer and a first capacitor. The load circuit together with the primary winding of the transformer and the first capacitor are shunted by a second transistor. A first secondary winding of the transformer forms part of a control circuit of the first transistor, while a second secondary winding of the transformer forms part of a control circuit of the second transistor. A combination of an auxiliary capacitor, an auxiliary transistor and a first timing circuit is provided to level the conduction times of the first and second transistors, a main electrode of the auxiliary transistor being connected to a junction between the first transistor and the second transistor.
A known DC/AC converter of the kind mentioned is described, for example, in U.S. Pat. No. 4,429,359. The converter described therein is a frequency converter of the bridge type. A disadvantage of this known DC/AC converter is that individual differences between the first and second transistor as to the time duration of the dissipation of charge carriers ("storage time") are not levelled when these transistors become non-conducting. This means that in general one transistor will always conduct for a slightly longer time than the other transistor. When energizing the afore-mentioned metal vapour discharge tube, this leads inter alia to a displacement of the metal participating in the discharge to one of the electrodes of the tube (cataphoresis). Thus, the irradiation of this discharge tube is adversely affected.